The Symantec bunker was built by the UK government in the early 1990s
to shelter key utilities workers in the event of a nuclear attack and
was originally a reservoir. The entrance is set into a hill near
Winchester.

For photos of one of the UK's other leading security firms at work, click here for our look inside Sophos' Pentagon.

Published: November 25, 2005 -- 13:15 GMT (05:15 PST)

Caption by: Tom Espiner

The airlock door is monitored by a digital camera 24/7. CCTV cameras
give a 360 degree view of the outside of the bunker, and have 30 days
of digitally recorded back-up.

Published: November 25, 2005 -- 13:15 GMT (05:15 PST)

Caption by: Tom Espiner

Blast doors lead into the bunker. They were designed to minimise the
shock waves caused by a nuclear explosion. The air inside the bunker is
pressurised to 1.5 ppsi greater than the external air pressure, the
stop unfiltered air entering the bunker.

Published: November 25, 2005 -- 13:15 GMT (05:15 PST)

Caption by: Tom Espiner

The glassed-off room that is the Security Operations Centre.
Workstations are constantly manned by up to 15 analysts. Threats are
also monitored on the four flatscreens on the facing wall.

Published: November 25, 2005 -- 13:15 GMT (05:15 PST)

Caption by: Tom Espiner

Symantec collects information from their customers' intrustion
prevention and detections systems and their firewalls. This data is
analysed, and customers are told if they are under attack.

Malicious code can be dealt with in the bunker, or it can be
escalated to Symantec's security response centre in Dublin. Symantec's
global infrastructure is in constant communication, and includes labs
in Calgary, Dublin and Auckland.

Published: November 25, 2005 -- 13:15 GMT (05:15 PST)

Caption by: Tom Espiner

Symantec filters 1.5 billion lines of potentially malicious code per
day, and collates information from email honeypots as well as customer
desktops and servers.

Published: November 25, 2005 -- 13:15 GMT (05:15 PST)

Caption by: Tom Espiner

All workers must sign in and out at this terminal when entering and
leaving the bunker. All visitors must be announced at least 24 hours
beforehand, and this extends to Symantec employees without the
necessary security clearance.

Published: November 25, 2005 -- 13:15 GMT (05:15 PST)

Caption by: Tom Espiner

The view out of the bunker towards the airlock, with door-locks on the
left. The doors can be closed, and the air inside filtered in the event of the external atmosphere becoming toxic.

Photos: The Symantec bunker

ZDNet UK has taken a trip inside Symantec's nuclear bunker to get a peek at how it fights the menace of cybercrime

Read MoreRead Less

All workers must sign in and out at this terminal when entering and
leaving the bunker. All visitors must be announced at least 24 hours
beforehand, and this extends to Symantec employees without the
necessary security clearance.